Browsing by Subject "In vitro model"

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    A scaffold-free multicellular three-dimensional in vitro model of osteogenesis
    (Springer, 2011) Gurkan, Umut A.; Kishore, Vipuil; Condon, Keith W.; Bellido, Teresita M.; Akkus, Ozan; Anatomy, Cell Biology and Physiology, School of Medicine
    In vitro models of osteogenesis are essential for investigating bone biology and the effects of pharmaceutical, chemical, and physical cues on bone formation. Osteogenesis takes place in a complex three-dimensional (3D) environment with cells from both mesenchymal and hematopoietic origins. Existing in vitro models of osteogenesis include two-dimensional (2D) single type cell monolayers and 3D cultures. However, an in vitro scaffold-free multicellular 3D model of osteogenesis is missing. We hypothesized that the self-inductive ossification capacity of bone marrow tissue can be harnessed in vitro and employed as a scaffold-free multicellular 3D model of osteogenesis. Therefore, rat bone marrow tissue was cultured for 28 days in three settings: 2D monolayer, 3D homogenized pellet, and 3D organotypic explant. The ossification potential of marrow in each condition was quantified by micro-computed tomography. The 3D organotypic marrow explant culture resulted in the greatest level of ossification with plate-like bone formations (up to 5 mm in diameter and 0.24 mm in thickness). To evaluate the mimicry of the organotypic marrow explants to newly forming native bone tissue, detailed compositional and morphological analyses were performed, including characterization of the ossified matrix by histochemistry, immunohistochemistry, Raman microspectroscopy, energy dispersive X-ray spectroscopy, backscattered electron microscopy, and micromechanical tests. The results indicated that the 3D organotypic marrow explant culture model mimics newly forming native bone tissue in terms of the characteristics studied. Therefore, this platform holds significant potential to be used as a model of osteogenesis, offering an alternative to in vitro monolayer cultures and in vivo animal models.
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    Population model analysis of chiral inversion and degradation of bupropion enantiomers, and application to enantiomer specific fraction unbound determination in rat plasma and brain
    (Elsevier, 2021) Bhattacharya, Chandrali; Masters, Andrea R.; Bach, Christine; Stratford, Robert E., Jr.; Medicine, School of Medicine
    Pharmacologic effects elicited by drugs most directly relate to their unbound concentrations. Measurement of binding in blood, plasma and target tissues are used to estimate these concentrations by determining the fraction of total concentration in a biological matrix that is not bound. In the case of attempting to estimate R- and S-bupropion concentrations in plasma and brain following racemic bupropion administration, reversible chiral inversion and irreversible degradation of the enantiomers were hypothesized to confound attempts at unbound fraction estimation. To address this possibility, a kinetic modeling approach was used to quantify inversion and degradation specific processes for each enantiomer from separate incubations of each enantiomer in the two matrices, and in pH 7.4 buffer, which is also used in binding experiments based on equilibrium dialysis. Modeling analyses indicated that chiral inversion kinetics were two to four-fold faster in plasma and brain than degradation, with only inversion observed in buffer. Inversion rate was faster for S-bupropion in the three media; whereas, degradation rates were similar for the two enantiomers in plasma and brain, with overall degradation in plasma approximately 2-fold higher than in brain homogenate. Incorporation of degradation and chiral inversion kinetic terms into a model to predict enantiomer-specific binding in plasma and brain revealed that, despite existence of these two processes, empirically derived estimates of fraction unbound were similar to model-derived values, leading to a firm conclusion that observed extent of plasma and brain binding are accurate largely because binding kinetics are faster than parallel degradation and chiral inversion processes.